Georges Lemaître (1894-1966), both priest and physicist, is the founding father of the big bang theory. In 1951, pope Pius XII saw in Lemaître’s theory a confirmation of the Christian doctrine of creation. Surprisingly enough, Lemaître opposed this official statement of the pope. According to him, a cosmological theory cannot be used as a proof nor as a refutation of an article of faith. In my research I investigate which vision Lemaître had on the relation between religion and science. This research puts the current-day discussion about religion and science in a surprisingly new light.